VB.NET

Connect to IMAP Through an SSH Tunnel

Demonstrates the Chilkat Imap.SshOpenTunnel method, which connects to an SSH server and prepares a tunnel through which a later IMAP connection is routed. The first argument is the SSH server hostname and the second is the SSH port (usually 22). After it succeeds, authenticate the tunnel, then call Connect and Login for the IMAP server.

Background: SSH tunneling (port forwarding) routes the IMAP session inside an encrypted SSH connection. It is used to reach a mail server that is only accessible from behind a bastion/jump host, or to add a second layer of transport security. The order is fixed: open the tunnel, authenticate to SSH, then connect and log in to IMAP — and close the tunnel with SshCloseTunnel when finished.

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Dim success As Boolean = False

'  Demonstrates the Imap.SshOpenTunnel method, which connects to an SSH server and prepares a
'  tunnel for a later IMAP connection.  The 1st argument is the SSH server hostname and the
'  2nd is the SSH port (usually 22).

Dim imap As New Chilkat.Imap

'  Open the SSH tunnel.  Port 22 is the usual SSH port.
Dim sshPort As Integer = 22
success = imap.SshOpenTunnel("ssh.example.com",sshPort)
If (success = False) Then
    Debug.WriteLine(imap.LastErrorText)
    Exit Sub
End If


'  The SSH password is not hard-coded in source.  Insert code here to obtain it from an
'  interactive prompt, environment variable, or a secrets vault.
Dim sshPassword As String

'  Authenticate the SSH tunnel with a username and password.
success = imap.SshAuthenticatePw("sshUser",sshPassword)
If (success = False) Then
    Debug.WriteLine(imap.LastErrorText)
    Exit Sub
End If


'  With the SSH tunnel in place, connect and log in to the IMAP server as usual.  The IMAP
'  traffic flows through the tunnel automatically.
imap.Ssl = True
imap.Port = 993
success = imap.Connect("imap.example.com")
If (success = False) Then
    Debug.WriteLine(imap.LastErrorText)
    Exit Sub
End If

success = imap.Login("user@example.com","myPassword")
If (success = False) Then
    Debug.WriteLine(imap.LastErrorText)
    Exit Sub
End If


success = imap.Disconnect()
If (success = False) Then
    Debug.WriteLine(imap.LastErrorText)
    Exit Sub
End If


'  Close the tunnel when finished with the IMAP connection.
success = imap.SshCloseTunnel()
If (success = False) Then
    Debug.WriteLine(imap.LastErrorText)
    Exit Sub
End If